Start measurement instantly when running the VI

[Data-acquisition]

Dear all,

I need to mearsure frequences as soon as I Run the Vi even there is no source inputed, which means I shoud acquire 0 when there is no pulse being inputed.

Thank you very much for your reply. Any hint or advice would be greatly appreciated.

Shang

[Data-acquisition]

Maybe I should express my opinion in another way.

Dear all,
We all know that the CI frequency task will not start until some pulses come. My problem is how to start it when there is no pulse to be inputed externally. Is creating one internal pulse to trigger the CI task the right way? Will this task stop when there is not pulse following the initial trigger? 

Any help is much appreciated.

Thanks!